The Perils of Purchased IP
When building a complex SOC, only those in enormous organizations have luxury of designing every bit of the chip. The rest of us rely on purchasing IP. No one thinks twice about using a digital cell library from an outside source, or a padcells for the padring. Using PLLs and Phys are fairly commonplace too. Less common but not unheard of are data converters and power management circuits, regulators and the like.
At various times during my career I’ve worked on projects where the purchase and integration of IP was part of the plan. I have acquired a wide variety of IP, from many vendors and I have had both good experiences and bad ones. Over-generalizing somewhat, the good experiences tended to happen when my team and I were able to peak inside the “black box”, to review the schematics and layouts of the IP and to run our own simulations. Conversely, bad experiences happened when the IP is delivered without schematics and with only the vendor’s promise that the design was “silicon proven”.
Choosing only silicon-proven IP for inclusion in your design is of course a good strategy to avoid design flaws and integration hassles with a new piece of IP. Since so many customers insist on buying silicon proven IP, vendors are eager to provide that assurance, even to the point of claiming it when it isn’t really true. In one extreme case that I am familiar with, a vendor claimed a circuit was silicon proven but in fact the silicon had actually been run on an different technology node and was a different version of the design than was purchased by the customer. The differences in the versions included a significant architectural change. The customer wasn’t given a true sense of the situation until his team we busy debugging a piece of silicon that didn’t work. Unfortunately, if an IP vendor can stretch the truth about the maturity of their design, just to make a sale, some will do so.
Over the next few posts I will outline the various things that an IP user should do to avoid product silicon that doesn’t function properly. I will also discuss various changes that IP vendors could make to their delivery model to help their customers succeed.
One thing is true: when you purchase IP, the only thing you really “own” are the problems.